This proposal is to fund a complete refurbishment of the McLean Hospital 4 Tesla Varian Whole Body Multinuclear Magnetic Resonance Imaging system. This instrument has been extremely productive since it was first installed in May, 2001 both as a development platform for new spectroscopy techniques, and as the means for applying these techniques in several thousand subjects for NIH funded projects. However, the rapid pace of technical development in the MR field means that recent advances in the field are difficult or impossible to implement on the current hardware. This is especially relevant as we are building a translational program at McLean that will partner the 4T with a new, 9.4T Varian animal scanner (currently being installed), where we expect to develop techniques that may be useful in humans. Our current 4T scanner, particularly the console hardware and user interface, once at the forefront of technology, has become dated. This has manifested itself in increasing unreliability and downtime, continued requirements for both extensive user training, and time-consuming interventions from staff physicists to repair and maintain the system. The proposed upgrade will replace the heart of the spectrometer;the signal generation, measurement, processing and interface components. The magnet, gradients, shim supply and power amplifiers, remain in excellent working order and will be retained. This offers a unique opportunity to acquire a state of the art MR spectrometer at a fraction of the cost of a new unit, by leveraging the value of the existing magnet and sitting infrastructure. Since 2001, there have been significant technical advances in all aspects of Varian's MR console hardware;digital radiofrequency receiver hardware gives much higher detection sensitivity of rare compounds, better time stability in long acquisitions, and sharper filtering with minimal phase roll, which significantly improves spectral quantitation. A new RF front end improves noise figure and enables more flexible transmit receive configurations. Parallel RF transmission and reception improves RF homogeneity, can reduce power deposition, and can increase SNR and speed image and MRSI acquisition through the use of phased array and SENSE techniques. Revised grounding topology further improves SNR. Finally, the new, faster workstation improves acquisition and processing efficiency. Relevance: The McLean 4T scanner is one of the leading sites in the US for performing multinuclear MR spectroscopy in humans;we routinely employ 1H, 31P, 7Li, 23Na, 19F and 13C spectroscopy to study a wide range of psychiatric and substance abuse disorders. Multinuclear MR spectroscopy is an extremely important tool for evaluating new therapies for these disorders;this upgrade will keep this scanner at the forefront of the field, and will open up new opportunities for rapidly translating discoveries made in other animals to humans. PUBLIC HEALTH RELEVANCE This proposal is to fund a complete refurbishment of the McLean Hospital 4 Tesla Varian Whole Body Multinuclear Magnetic Resonance Imaging system. This scanner is one of the leading sites in the United States for performing multinuclear MR spectroscopy in humans;we routinely employ 1H, 31P, 7Li, 23Na, 19F and 13C spectroscopy to study a wide range of psychiatric and substance abuse disorders. Multinuclear MR spectroscopy is an extremely important tool for evaluating new therapies for these disorders;this upgrade will keep this scanner at the forefront of the field, and will open up new opportunities for rapidly translating discoveries made in other animals to humans.